OFFSET
1,1
REFERENCES
E.I. Ignatjew, Mathematische Spielereien, Urania Verlag Leipzig-Jena-Berlin, 2. Auflage 1982
EXAMPLE
a(1) = 50; 2^50 = 1125899906842624
a(2) = 51; 2^51 = 2251799813685248
a(3) = 25; 2^25 = 33554432
a(10) = 1558; 2^1558 = 10109583053...744
PROG
(PARI) double(n, k)=n\=10^(#Str(n)-2*k); if(n%10^k==n\=10^k, n)
a(n)=my(s=#Str(n)); for(k=1, 1e6, if(double(1<<k, s)==n, return(k)))
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Dec 14 2009
EXTENSIONS
More terms, program, and editing by Charles R Greathouse IV, Aug 02 2010
STATUS
approved